In a communications system, information, such as control information or data information, is usually transmitted between communications devices (for example, between a base station and a terminal) in the form of information sequences. Because the environment for wireless propagation is complex and varied, transmitted information sequences are susceptible to interference, and errors may occur. To reliably send the information sequences, a device at a transmitting end performs processing such as cyclic redundancy check (CRC), segmentation and check, channel coding, rate matching, and interleaving on the information sequence, and maps interleaved coded bits into modulation symbols and sends the modulation symbols to a device at a receiving end. After receiving the modulation symbols, the communications device at the receiving end correspondingly restores the modulation symbols to the information sequence through de-interleaving, de-rate matching, decoding, concatenation, and CRC. These processes can reduce transmission errors, and improve data transmission reliability.
New channel coding schemes, such as low-density parity-check (LDPC) code, polar code, etc., have been considered to be introduced into the fifth generation (5G) mobile communications system to improve performance. The LDPC code is a type of linear block code with a sparse check matrix, and is characterized by a flexible structure and low decoding complexity. Because decoding the LDPC code uses partially parallel iterative decoding algorithms, the LDPC code has a higher throughput than a conventional turbo code. An LDPC code frequently used in the communications system has a special structural feature, and a base matrix of the LDPC code has m*n elements. If using a lifting factor z for lifting (expansion), a parity check matrix H with (m*z)*(n*z) elements may be obtained. In other words, the parity check matrix H includes m*n block matrices. Each block matrix is either a z*z all-zero matrix or a block matrix obtained by circularly shifting an identity matrix. The lifting factor z is usually determined based on a code block size supported by the system and an information data size.
As different channel coding schemes are used, the communications system has different coding capabilities and decoding capabilities. How to process an information sequence to meet a channel coding requirement, so as to improve system coding performance and decoding performance becomes a problem to be resolved.